Volumetric behavior and solution microstructure of methanol-water mixture in sub- and supercritical state via density measurement and MD simulation

Densities of methanol-water mixtures at 350°C and 20-35MPa were measured with a laser-doppler vibrating densimeter. Excess molar volumes of methanol-water mixtures changed from negative to positive as methanol composition increased from X_m=0 to X_m=1. The composition dependence of the aqueous solution at high temperature and pressure was investigated from the microscopic viewpoint using molecular dynamics calculations. Characteristic changes, which imply that intermolecular interactions change from relatively attractive to relatively repulsive, were observed in the trends of the radial distribution function, internal energy and self-diffusion coefficients are corresponding to volumetric behavior.